Extended Data Fig. 1: DFT calculations for competing Diels-Alder and hetero-Diels-Alder pathways.
From: Efficient Lewis acid catalysis of an abiological reaction in a de novo protein scaffold
a, Diels-Alder and hetero-Diels-Alder reactions of the azachalcone 1 and 3-vinylindole 2 in SMD water [calculated at the ωB97X-D/6-311 + +g(2d,p)/SMD(water)//ωB97X-D/6-311 G(d,p)/SMD (water) level]. TS1-endo is ambimodal and affords both 3-endo and 4-endo. Experimentally, only 3-exo and 4-endo are observed. b, The endo hetero-Diels-Alder reaction of 1 and 2 in the presence of [Zn(OH)(H2O)2]+, calculated at the ωB97X-D/6-311 + +G(2d,p)/SMD(water)//ωB97X-D/6-311 G(d,p)/ SMD(water) level (the LANL2DZ and SDD effective core potentials were used for Zn in geometry optimisation and single energy calculations, respectively), occurs via a stepwise mechanism that favours formation of 4-endo. Relative enthalpies (H) and free energies (G) are shown in blue and red, and are reported in kcal/mol. Labelled distances are in ångströms.
